There has been known a plating apparatus that performs plating of a substrate surface by immersing a substrate such as a semiconductor wafer, held by a substrate holder, in a plating solution. In this type of plating apparatus, after the plating, the substrate holder, holding the substrate, is immersed in a cleaning liquid, such as pure water, stored in a cleaning bath to clean the substrate and the substrate holder. By immersing the substrate holder, holding the substrate, in the cleaning liquid in this manner, a liquid chemical such as the plating solution, adhering to the substrate and the substrate holder, is removed from them by basically diffusion due to a difference in the concentration between the liquids. The cleaning liquid in which the liquid chemical, such as the plating solution, has been diffused is discharged from the cleaning bath, so that one cleaning cycle using the cleaning liquid is completed. This cleaning cycle is repeated multiple times.
The cleaning bath for use in such post-plating cleaning of a substrate and a substrate holder generally has a shape of an open-top box with a constant opening area. Dimensions (i.e., a thickness, a width, and a depth) of the interior space of the cleaning bath are set to be large enough to prevent contact of the substrate holder with the cleaning bath when the substrate holder is introduced into the cleaning bath and the substrate holder is raised from the cleaning bath, taking into consideration the maximum thickness, the maximum width, and the immersion depth of the substrate holder.
An amount of the cleaning liquid, such as pure water, to be used in one cleaning cycle is determined by the volume of the cleaning bath that is determined from the product of the opening area and the depth of the cleaning bath. The total amount of the cleaning liquid to be used in a cleaning process consisting of multiple cleaning cycles, excepting an extra amount of the cleaning liquid to be supplied for the purpose of overflowing and an additional amount of the cleaning liquid to be supplied e.g., from a shower head, is equal to the product of the number of cleaning cycles and a value obtained by subtracting the volume of the substrate holder from the interior volume of the cleaning bath.
The applicant has proposed a substrate plating apparatus in which a narrow flow passage (processing chamber) is formed between an openable/closable lid provided in a cleaning bath and a substrate held in a bath body (see Japanese Laid-Open Patent Publication No. 2000-58496). A plating solution is passed through the flow passage while allowing the plating solution to flow along a surface of the substrate.
An apparatus has been proposed which, in order to reduce the use of a processing fluid, introduces the processing fluid into a narrow space between two plates which are movable in directions closer to and away from each other (see Japanese Laid-Open Patent Publication No. 2002-535831 (Translation of PCT Application)). A cleaning apparatus has been proposed which introduces a cleaning liquid into a cleaning chamber in which a cleaning object is set, and performs cleaning of the cleaning object while repeating pressurization and depressurization of the cleaning liquid (see Japanese Laid-Open Patent Publication No. 2004-14642).
Further, an apparatus has been proposed in which a processing object, which is suspended in a vertical position by a transport device, is surrounded by a surrounding means, and the processing object is cleaned by supplying a processing liquid into the surrounding means (see Japanese Laid-Open Patent Publication No. 2008-223094).
A substrate holder is configured to hold a substrate while sealing a gap between a peripheral portion of the substrate and the substrate holder with a sealing member. The substrate holder is immersed in a plating solution while holding the substrate. In general, the front surface of the substrate holder, holding the substrate, is not flat. Irregularities, including a fairly large recess having a diameter which is approximately equal to the diameter of the substrate, are formed in the front surface of the substrate holder holding the substrate. The front surface of the substrate holder thus has an uneven configuration. When such substrate holder holding the substrate is placed in a box-like cleaning bath so that the substrate and the substrate holder are cleaned with a cleaning liquid such as pure water, a large amount of the cleaning liquid flows into the recess formed by the substrate and the substrate holder, resulting in an increase in the amount of the cleaning liquid used. Further, according to this cleaning method, the use of cleaning liquid increases as the size of substrates increases.
A substrate holder, including a structure for sealing a gap between a peripheral portion of a substrate and the substrate holder, has a certain degree of thickness. When cleaning such a substrate holder with the use of the above-described box-like cleaning bath which is designed taking into consideration the maximum thickness, the maximum width, and the immersion depth of the substrate holder, it is necessary to use a cleaning liquid in a large amount. This problem will be more significant for substrates of a larger size. In the case of immersion cleaning using such a cleaning bath, it takes some time to store a cleaning liquid into the cleaning bath and to discharge the cleaning liquid from the cleaning bath in one cleaning cycle. Accordingly, when a cleaning process is performed by repeating the cleaning cycle multiple times, it takes a long time to complete the cleaning process.
None of the above-referenced patent documents are directed to a cleaning technique for cleaning a substrate holder, holding a substrate, with a cleaning liquid in a cleaning bath, the substrate holder being configured to hold the substrate while sealing a peripheral portion of the substrate with a sealing member, and having been subjected to plating of the substrate by immersing the substrate holder, holding the substrate, in a plating solution.
In the apparatus disclosed in the above-referenced Japanese Laid-Open Patent Publication No. 2008-223094, a processing liquid is supplied into the interior space of the surrounding member, having larger dimensions than the maximum width and the maximum thickness of a processing object and the transport device, without taking the uneven exterior configuration of the transport device into consideration. Therefore, the processing apparatus requires the use of a large amount of the processing liquid. In addition, a processing object is cleaned with the processing liquid while circulating the processing liquid. Therefore, the processing liquid can become contaminated gradually, resulting in insufficient cleaning of the processing object.